The present invention concerns a control system for machine tools or the like, and more particularly to a control system for machine tools which regulate spindle bearing lubrication in accordance with bearing temperature and which regulates the spindle bearing preload and the spindle axis feedrate in accordance with spindle bearing thrust to assure optimum machine tool performance.
Rotating machinery, such as machine tools, or the like, usually include one or more ball bearings or roller bearings for journaling a rotating member such as a spindle as in the case of a machine tool, to a stationary member such as the machine tool spindlehead. It is well known to those skilled in the art that friction between ball bearing and roller bearing contact surfaces is best reduced by lubricating the bearing with a fluid lubricant, either a single fluid, such as oil or air or a lubricating fluid mixture such as an oil-air mist mixture. An oil-air lubricating mist mixture is particularly advantageous since the air in the oil-air lubrication mist mixture serves to carry away bearing heat while the oil provides appropriate lubrication for bearing contact surfaces, thereby assuring long bearing life.
One of the difficulties incurred in employing an oil-air mist mixture to lubricate ball bearings and roller bearing has been regulation of the amount or volume of oil in the oil-air lubrication mist mixture as percentage of total mixture volume. Too little oil in the oil-air lubrication mist mixture results in insufficient bearing lubrication and hence premature bearing wear. On the other hand, too much oil in the lubrication mist mixture may cause the bearings to clog and overheat thereby greatly reducing bearing life.
Heretofore, regulation of the percentage volume of oil in an oil-air bearing lubrication mist mixture has been achieved by open loop regulation, that is, by manually presetting the oil and air mixing valves. Needless to say, should the speed or axial thrust of the rotating member journaled to the bearing suddenly change, then the percentage volume of oil in the oil-air bearing lubrication mist mixture must also be changed. Otherwise, bearing damage may result if too little or too much oil is present in the bearing lubrication mist mixture. Additionally, should a valve clog, or if the flow of oil becomes intermittent, then there may also be an insufficient volume of oil in the oil-air mist mixture. The present invention concerns a control apparatus for rotating machinery which automatically regulates the percentage volume of oil in the oil-air lubrication mist mixture supplied to lubricate rotating machinery ball and roller bearings.
It is an object of the present invention to provide a control apparatus for regulating the lubrication provided to rotating machinery bearings.
It is another object of the present invention to provide a control apparatus for automatically regulating the lubrication provided to machinery bearings in accordance with bearing temperature to assure reduced bearing temperature thereby extending bearing life.
It is yet another object of the present invention to provide a machine tool control apparatus for automatically regulating spindle bearing lubrication in accordance with spindle bearing temperature and for regulating the spindle bearing preload and the spindle axis feedrate in accordance with radial and axial spindle deflection.